Crushers for crushing materials to be crushed such as unnecessary cast product, sprue, runner and ingate have been conventionally known. In the case where these unnecessary materials to be crushed are crushed, crushers are convenient also, for example, in storing, transporting and treating the waste after crushing if they can finely crush the materials. Therefore, blades, which are used in crushers, are especially important in order to realize efficient crushing of the materials to be crushed. For example, Document 1, which will be described below, is indicated as one example of documents regarding crushers for crushing unnecessary materials to be crushed.